1. Field of the Invention
The present invention relates to a liquid mixing apparatus that is usable in, for example, a small chemical analysis/synthesis system that performs chemical analysis and chemical synthesis at chip. More particularly, the present invention relates to a liquid mixing apparatus that makes use of induced charge electroosmosis.
2. Description of the Related Art
A micropump making use of electroosmosis is used in the field of, for example, Micro-Total Analysis System (μTAS) because, for example, the micropump is easily mounted in a very small flow channel (micro flow channel) having a relatively simple structure.
Accordingly, in recent years, a micropump making use of induced-charge electroosmosis (ICEO) is becoming the focus of attention because, for example, this type of micropump can increase the fluid rate of a liquid and can suppress chemical reaction occurring between an electrode and a liquid since AC driving can be performed.
U.S. Pat. No. 7,081,198 (hereunder may also be referred to as “Patent Document 1”) and M. Z. Bazant and T. M. Squires, Phys. Rev. Lett. 92, 066101 (2004) (hereunder may also be referred to as “Non-Patent Document 1”) each discuss a micromixer making use of induced-charge electroosmosis and a vortex flow caused by an ICEO flow around a circular cylindrical metallic post.
H. Zhao and H. Bau, Phys. Rev. E 75066217 (2007) (hereunder may also be referred to as “Non-Patent Document 2”) discuss a mixing apparatus that alternately switches between two vortex flows by alternately applying a vertical electric field and an oblique electric field to a circular cylindrical metallic post.
In a very small flow channel, mixing by turbulent flow cannot be expected because the Reynolds number is low. Therefore, the mixing is primarily carried out by making use of molecular diffusion.
Consequently, in the micromixers that are discussed in Patent Document 1 and Non-Patent Document 1 and that cause vortices to be generated in micro flow channels by ICEO flow, time is required for achieving sufficient mixing and the required flow channel lengths are relatively long.
In contrast, in the mixing apparatus discussed in Non-Patent Document 2, an oblique electric field that is tilted in an oblique direction from a wall surface of a flow channel is required. Therefore, if one actually attempts to form the device, electrode arrangement needs to be considered. As a result, it may be difficult to achieve reduced size and integration.